I saw a thread titled “Inconsistent iPhone Presence” so I wanted to start a new thread because the Android development might be separate from the IOS development and I don’t want this to be buried in the comments.
Just like the Apple people report, though, I find the mobile presence feature to be hit-or-miss. I am sitting 20 miles from home, comfortably outside the fence I set up 
And yet the Smartthings app on my phone has not recognized I have left. Yes, the GPS is on, and in any event I’m sure my phone knows roughly where I am thru wifi signals. Its only when I restart the app that my location gets updated. This seems to happen periodically (eg this isn’t the first time, its one of several). The reverse also happens. When I arrive home the Smartthings app often fails to recognize this.
As a consequence my home security system basically doesn’t work unless I manually go into the Smartthings app and set my presence to “away”. Not exactly the automation I was hoping for. And when I arrive home since Smartthings doesn’t know I’m there it sets off the siren. Again, not exactly desired behavior.
Has anybody found a fix for inconsistent mobile presence detection? Is all I can do restart the app whenever I leave or arrive?
One thing I would do, if Smartthings would add hooks to Tasker, is have Tasker realize I am away and change the presence location. Tasker is generally reliable and would be perfect for this workaround.